Fatigue crack growth modeling considering a hybrid propagation strategy

Abstract

Fatigue results from the occurrence of several damage mechanisms and their interactions. The cyclic plastic strain and damage accumulation at the crack tip are widely pointed as the main agents behind fatigue crack growth (FCG). In this work, the authors propose the prediction of FCG through a node release numerical model that offers several possibilities regarding the modeling of the mechanisms behind fatigue. A hybrid propagation method is presented where both cumulative plastic strain and porous damage represent parallel propagation criteria. Accordingly, the node is released once either a critical plastic strain or a critical porosity, at the crack tip, is reached. The Gurson–Tvergaard–Needleman (GTN) damage model is employed to predict porous damage evolution through the processes of nucleation and growth of micro-voids. The model is validated through comparison with experimental data for the AA2024-T351 aluminum alloy. Finally, the interactions between plastic strain, porous damage, crack closure, and stress triaxiality are accessed.